Aquatic Extruded Feed Production Process

With the continuous development of modern aquaculture toward higher efficiency and environmental sustainability, extruded aquatic feed has become one of the mainstream products in the feed industry. Thanks to its balanced nutrition, excellent water stability, high digestibility, and reduced impact on the aquatic environment, it has gained wide recognition in the market.

For feed manufacturers, a scientific and well-designed production process is not only the foundation for producing high-quality feed, but also an important guarantee for increasing production capacity, reducing energy consumption, and improving market competitiveness.

Due to the wide variety of aquatic feed formulations, changing raw materials, strict grinding fineness requirements, and poor material flowability, the production process for aquatic extruded feed is relatively demanding. A typical process generally includes raw material receiving, grinding and mixing, conditioning and extrusion, drying, coating, cooling, grading, and packaging.

1. Raw Material Receiving, Cleaning, and Coarse Grinding

Raw materials used in feed mills are generally divided into powder materials and granular materials.

Powder materials do not require coarse grinding. After unloading, they are conveyed to a cleaning sieve for impurity removal and then pass through a magnetic separator before entering the batching bins for primary formulation.

Granular materials require coarse grinding. After cleaning and magnetic separation, the materials enter a pre-grinding bin and are coarsely ground before being transferred to the batching bins.

Coarse grinding serves as a pretreatment step before fine grinding. Its purpose is to reduce particle size variations, improve the operating condition and efficiency of the fine grinding system, and ensure stable product quality.

2. Primary Batching and Mixing

Primary batching mainly handles bulk ingredients with a relatively high proportion in the formula. Electronic batching scales are commonly used for accurate dosing.

After batching, the materials enter the first mixing stage. This pretreatment process helps minimize particle size variation, improve grinding performance, increase grinding efficiency, and ensure product consistency.

3. Secondary Grinding

Aquatic animals generally have low feed intake, short digestive tracts, and limited digestive capability. Therefore, aquatic feed requires very fine particle sizes.

For example, shrimp feed normally requires all particles to pass through a 40-mesh screen, with less than 5% retained on a 60-mesh screen. As a result, a secondary grinding process is necessary.

After the first mixing stage, the materials are elevated into a grinding bin and then enter the secondary grinding system. Following fine grinding, the materials pass through a rotary grading sieve to remove fibrous particles generated during grinding.

4. Secondary Mixing

After secondary batching, the ingredients enter the secondary mixer.

A manual addition port is provided for micro-ingredients, while liquid addition systems are used for oil and water addition.

All ingredients must be mixed thoroughly, with a coefficient of variation (CV) below 5%, ensuring excellent feed uniformity.

After ultra-fine grinding and secondary mixing, the materials proceed to the extrusion process.

5. Conditioning and Extrusion

During extrusion, the material is subjected to high temperature, high moisture, and high pressure conditions for a certain period.

In this process, significant physical and chemical changes occur, including starch gelatinization and protein denaturation. As the material exits the die, the pressure drops instantly, causing moisture to vaporize and expand the product, forming extruded feed.

Compared with conventional pellets, extruded feed offers several advantages:

• Better palatability;

• Prevention of ingredient segregation;

• Easier transportation;

• Higher starch gelatinization and protein digestibility;

• Reduced feed waste and improved feed conversion efficiency;

• Excellent floating performance for floating feed, allowing easier observation of feeding activity and minimizing water pollution.

6. Drying

After extrusion, the pellets are soft and contain approximately 25–30% moisture. Therefore, they must enter the dryer to reduce the moisture content to the target level.

Pneumatic conveying is generally recommended to minimize pellet breakage. The drying system uses circulating hot air to ensure sufficient heat exchange and uniform moisture evaporation, thereby improving pellet hardness and structural stability.

An optimized drying process helps maintain product appearance and nutritional value while extending shelf life and ensuring stable operation for subsequent processes.

7. Coating

After drying, the pellets enter the coating system, where oil, vitamins, attractants, and other nutrients are applied to the pellet surface.

This coating process provides additional energy for aquatic animals, minimizes the loss of heat-sensitive ingredients, improves feed palatability, and reduces fines generation.

8. Cooling

After coating, the pellet surface is uniformly covered with oil, attractants, and heat-sensitive nutrients. The material then enters the cooling section.

The cooling system uses ambient air to exchange heat with the pellets, gradually reducing their temperature to near room temperature while removing residual moisture.

Proper cooling prevents agglomeration, mold growth, and quality deterioration during packaging and storage, ensuring product stability and longer shelf life.

9. Grading and Packaging

After cooling, the material is conveyed to the grading system.

Typically, a grading sieve consists of two screen layers:

• Oversized particles from the upper screen are returned to the crusher for reprocessing.

• Fine particles collected from the lower screen are recycled to the extrusion system.

• Qualified pellets retained on the screen are conveyed to the finished product bin for weighing and packaging.

Conclusion

The above process represents a mature and widely adopted configuration for aquatic extruded feed production. It offers stable performance and broad adaptability.

By adjusting formulations and processing parameters, the system can produce sinking feed, slow-sinking feed, and floating feed to meet the requirements of different aquatic species.

It is widely used in the production of feed for fish, shrimp, crab, and other specialty aquatic species.